In reality, that message almost always means that the Essbase app has crashed. Take a look at the application log.

Evidently the Arbor development team decided that the obvious explanation for an application's failure to respond was network interruption, with the possibility of a crash too remote even to mention. If you didn't laugh, you'd cry...

you could have corruption in the .pag file. You might want to run a verify against the database (look up alter Database zzzz.xxxxx validate using default error_file. If it finds errors then try
Alter database zzzz.xxxxx Repair invlaid_block_headers